Ethanol templated synthesis of microporous/mesoporous nanozinc oxide with multi-level structure and its outstanding photo-catalytic properties

Zinc oxide has been of interest because of its efficient redox capacity in the UV spectral region. However, the high bandwidth limits its application in the visible region. Although synthesizing heterojunctions and doping with other elements have become the focus of the problem, it inevitably has an impact on the environment. In contrast, the template method is not only environmentally friendly but also can be used to increase the degradation rate by changing the nanoparticle mesoporous structure. Microporous/mesoporous zinc oxide with multi-level structure was synthesized using anhydrous ethanol as a green templating agent in a mild and energy-efficient method. The prepared nZnO was characterized using XRD, SEM, BET, and HR-TEM. XRD confirmed that the formation of hexagonal wurtzite zincite nZnO with good crystallinity. SEM results showed that the products were flower-like structures composed of nanosheets with a thickness of 20 nm and an average diameter of 400 nm. TEM and BET confirmed the presence of pits with diameters ranging from about 1 nm to 20 nm existed on the surface of the nanosheets, while the specific surface area of 28.05 m2/g and the pore volume of 0.069 cm3/g also provide advantages for nZnO as a photocatalytic material. The synthesized nZnO overcame the disadvantage of responding only in the UV region, and the photocatalytic degradation efficiency of MB reached 93.2% after 60 min of xenon lamp irradiation, and stabilized at 86.15% after five photocycling tests. Compared with other kinds of templates, anhydrous ethanol has the advantages of environmental friendliness and simple post-processing, and it also provides ideas for the synthesis of multilevel structures of other nanomaterials.